The invention relates to a ventilation device and to a rail traction electric motor equipped with such a device.
In the field of rail traction, an electric motor is generally incorporated at a bogey, under the body of a locomotive or a carriage. As an electric motor can consume a significant amount of electrical power, it needs to be cooled so as to dissipate some of this power and it is known practice to use the ambient atmosphere to do this. However, the surroundings of rail traction motors are generally polluted, on the one hand, because of rubbish which may lie on the track and, on the other hand, because of rain or mud resulting from unfavourable weather conditions. For the above reasons, it is known practice for an electric motor to be protected from its environment by placing filters or gratings over the cooling air intake. It is also known practice for the motor cooling air to be drawn in through a length of trunking, from a region of lower pollution, such as an interior compartment of the train or a region near the roof of a locomotive. These measures introduce significant pressure drops along the path along which the cooling air flows, and this reduces its effectiveness and may lead to soiling of the motor.
Document FR-A-2,645,817 discloses the ventilating of a rail traction motor using air delivered by a fan, some of this air being discharged by centrifuging into an opening facing which there is a separator element. The heaviest particles are removed under the effect of centrifugal forces and are therefore not sent towards the interior volume of the motor. However, the effectiveness of the centrifuging depends essentially on the rotational speed of the inlet fan, which speed is linked to the running speed of the motor. This speed depends on the conditions of use of the motor, it being possible for a motor usually to run at a low speed, particularly in the case of an urban rail vehicle of the tramway or trolley bus type. Furthermore, the air discharged through the peripheral opening plays no part in cooling and the acoustic emissions may be generated by the discharge of part of the air stream directly into the ambient atmosphere.
It is these drawbacks which the invention more specifically sets out to overcome by proposing a ventilation device in which all of the air delivered by a fan is used to cool the motor while the risks of soiling or pollution are minimized.
With this in mind, the invention relates to a device for ventilating a rail traction electric motor, comprising a centrifugal fan capable of rotating in one or both directions, placed in an air inlet chamber and delivering air towards the motor, characterized in that the air stream delivered by the fan is split into an inner stream, directed towards the interior of a confinement space containing at least the rotor of the motor, and an outer stream directed towards ducts for cooling the stator of the motor.
By virtue of the invention, the air stream delivered by the inlet fan is used to cool both the rotor and the stator of the motor, that proportion of the air which is most likely to be contaminated with relatively heavy particles being directed, under the effect of centrifugal force, outwards, that is to say towards the ducts for cooling the stator, while the less contaminated proportion, which constitutes the inner stream, can be directed towards the interior of the confinement space without major risk of soiling the inside of the motor.
According to advantageous but not compulsory aspects of the invention, the device incorporates one or more of the following features:
The fan delivers into a feed nozzle for the ducts, a partition which separates the internal volume of this nozzle from the confinement space being pierced with at least one communication opening allowing the first stream to circulate. It is possible to provide several openings for communication between the internal volume of the nozzle and the space, these openings being distributed roughly uniformly around a central axis of the motor. It is also possible to envisage for this or these openings to be formed radially on the inside of the path defined by the nozzle for the second stream. By virtue of this aspect of the invention, the first stream of cooling air directed towards the space is xe2x80x9ctappedxe2x80x9d off the stream directed towards the ducts for cooling the stator, this tapping taking place at an internal face of the nozzle where the most contaminated air, that is to say the air most heavily laden with relatively heavy particles, is furthest away.
There is at least one outlet opening for the first air stream to leave the space. This outlet opening may be formed near the mouth of a duct for cooling the stator. In this case, a rib for separating the air streams leaving this opening and leaving this duct is advantageously provided.
A second fan generates or assists a flow of air inside the confinement space, from the inner stream. This second fan increases the movements of the air in the confinement space and thus improves the effectiveness of the cooling of the elements contained in this space.
The confinement space contains the rotor, an internal central part of the stator, at least one winding associated with this stator or with this motor, part of the central shaft of the motor and, possibly, a second fan. All of the aforementioned elements are thus cooled by the first air stream.
The invention also relates to a rail traction electric motor equipped with a ventilation device as defined hereinabove. Such a motor operates very satisfactorily, including in a contaminated environment, and its particularly effective cooling means that it may be envisaged for a high power motor according to the invention to be made relatively small in size.